Embedded multi-string well head shear

ABSTRACT

The present disclosure generally provides apparatus and methods for removing a subsea well head. The apparatus may include an embedded shear comprising a pile and a shear cutter integrated into the pile. The shear cutter may be mounted within the pile near a lower end thereof. The pile may include a well head conductor receptacle adapted to receive a subsea well head, and the shear cutter may include a shear blade that extends across the well head conductor receptacle when activated. 
     The method may include providing a pile with a shear cutter integrated therein, lowering the pile over the well head, pumping water out of the pile to drive the pile into the seafloor to a desired cutting depth, activating the shear cutter to cut off a portion of the well head, and pumping water into the pile to drive the pile out of the seafloor.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Application No. 61/252,043, filed on Oct. 15, 2009 and entitled “Embedded Multi-String Well Head Shear,” which is incorporated herein by reference for all purposes.

FIELD OF THE INVENTION

The present disclosure relates generally to the removal of subsea well heads, and in particular, to the removal of subsea well heads using an embedded multi-string well head shear.

BACKGROUND

Traditionally, subsea well heads have been removed by a variety of different methods, including with the aid of explosives, by using abrasive cutters internally, or by using shear tools externally that require first excavating a so-called “glory hole” deep enough to cut the well head about 15 feet or so below the mud line.

The use of explosives subsea is becoming less favored due to the negative environmental impact, especially as it relates to marine life. Internal abrasive cutters have a low success rate for multi-string conductors (i.e. concentric well casings with the annular space between them grouted with cement) due to the overall thickness of the steel pipe to be cut and the variable media (i.e. steel to cement and back to steel).

Multi-string shear tools, such as massive hydraulic shears, can externally sever an entire multi-string conductor in a single cut once a glory hole is formed that allows the well head to be cut below the mud line. However, excavating the glory hole requires an extensive amount of soil removal since the sides of the pit must be sloped back in order to maintain stability. Such an operation is very time consuming and expensive, and it also has a negative environmental impact.

SUMMARY OF THE DISCLOSURE

In one aspect, the present disclosure could generally provide an embedded shear that comprises a pile and a shear cutter integrated into the pile. The pile may be a suction pile. The pile may further comprise a pump interface. The shear cutter may be hydraulically actuated, and may further comprise hydraulic cylinders driven by external hydraulic power. In various embodiments, the external hydraulic power is supplied by one of a hydraulic umbilical, an accumulator bottle or a remotely operated vehicle hot stab. The pile may further comprise a well head conductor receptacle adapted to receive a subsea well head. In an embodiment, the shear cutter further comprises a shear blade that extends across the well head conductor receptacle when activated. The shear cutter may be mounted within the pile near a lower end thereof.

In another aspect, the present disclosure could generally provide a method for removing a subsea well head that comprises providing a pile with a shear cutter integrated therein, lowering the pile over the well head, pumping water out of the pile to drive the pile into the seafloor to a desired cutting depth, activating the shear cutter to cut off a portion of the well head, and pumping water into the pile to drive the pile out of the seafloor. In an embodiment, activating the shear cutter may comprise providing hydraulic power to hydraulic cylinders to drive a shear blade. The method may further comprise receiving the well head within a well head conductor receptacle of the pile while lowering the pile over the well head. In an embodiment, activating the shear cutter comprises driving a shear blade across the well head conductor receptacle to cut off the portion of the well head. The method may further comprise retaining the cut off portion of the well head within the well head conductor receptacle and/or raising the pile away from the seafloor while retaining the cut off portion of the well head therein.

In still another aspect, the present disclosure could generally provide a method for removing a subsea well head that comprises providing a pile with a shear cutter mounted internally near a lower end thereof, lowering the pile over the well head, embedding the pile into the seafloor to a desired cutting depth without excavating a glory hole, activating the shear cutter to cut off a portion of the well head, and removing the pile from the seafloor. The method may further comprise raising the pile away from the seafloor while retaining the cut off portion of the well head therein. In some embodiments, embedding the pile into the seafloor comprises pumping water out of the pile, and removing the pile from the seafloor comprises pumping water into the pile. The method may further comprise receiving the well head within a well head conductor receptacle of the pile while lowering the pile over the well head. In an embodiment, activating the shear cutter comprises driving a shear blade across the well head conductor receptacle to cut off the portion of the well head.

Other technical features may be readily apparent to one skilled in the art from the following figures, descriptions and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of this disclosure and its features, reference is now made to the following description, taken in conjunction with the accompanying drawings, in which:

FIG. 1A is schematic illustration of one embodiment of an embedded shear comprising a shear cutter apparatus integrated into, or mounted to, a suction pile;

FIG. 1B is a close vertical view from the bottom of the embedded shear apparatus depicted in FIG. 1A;

FIGS. 2A-D is a storyboard illustration of one embodiment of a method for removing a subsea well head.

DETAILED DESCRIPTION

Embodiments of the present disclosure generally provide apparatus and methods for removing subsea well heads, such as multi-string subsea well heads, by forcing an embedded shear apparatus into the seafloor to the required cutting depth without excavating a glory hole. In an embodiment, the embedded shear comprises a shear cutter apparatus associated with a pile that may be embedded into the seafloor by means of a suction system. The suction pile may provide a foundation for the shear cutter, as well as the motive force to embed the shear cutter to the required depth to cut the well head.

FIG. 1A is a schematic elevation view of one embodiment of an embedded shear 100 comprising a shear cutter apparatus 10 integrated into and/or mounted to a pile 20. In an embodiment, the shear cutter 10 is located at a lower end of the pile 20 and disposed internally thereof. The shear cutter 10 comprises a hydraulic cylinder 14 and a shear blade 15. In an embodiment, the pile 20 is a suction pile. The pile 20 may be generally cylindrical in shape and comprises an outer wall 21, a top cap 22, a pump interface 23, and a well head conductor receptacle 36. In an embodiment, the well head conductor receptacle 36 starts at the bottom of the pile and runs longitudinally within the interior of the pile 20 to receive and position the well head within the pile 20.

FIG. 1B is a close vertical view from the bottom of the embedded shear 100 of FIG. 1A. Protection grillage 37 is disposed across an open lower end of the pile 20, and support beams 38 run generally perpendicular to the protection grillage 37 to support the shear cutter apparatus 10 within the pile 20. This view also shows the relative positions of the hydraulic cylinders 14, the shear blade 15, and the well head conductor receptacle 36.

FIGS. 2A-D depict a storyboard of one embodiment of a method for removing a subsea well head 40 using the embedded shear 100 of FIGS. 1A and 1B. As depicted in FIG. 2A, the embedded shear 100 is positioned over a well head 40 extending above the seafloor 50 such that the well head 40 is aligned with the well head conductor receptacle 36 of the pile 20.

As the embedded shear 100 is lowered to receive the well head 40 into the well head conductor receptacle 36, the pile 20 embeds itself into the seafloor 50 as shown in FIG. 2B. In most cases, this initial embedded depth is not sufficient for cutting the well head 40, and therefore, the pile 20 may be further embedded into the seafloor 50 to position the shear cutter 10 to a satisfactory depth.

FIGS. 2B and 2C show the pile 20 being suction embedded into the seafloor 50 to achieve a satisfactory depth for the shear cutter 10. In particular, water is pumped out of suction pile 20 through pump interface 23 creating a pressure differential that drives the suction pile 20 further into the seafloor 50. Once a satisfactory depth is achieved, the shear cutter 10 is activated such that hydraulic cylinders 14 drive the shear blade 15 through the well head 40, as shown in FIG. 2C. In an embodiment, external hydraulic power may be provided to the cylinders 14 for activation. Potential means of providing such hydraulic power are typically via hydraulic umbilical, accumulator bottles or ROV (remotely operated vehicle) hot stabs.

FIG. 2D depicts how the suction pile 20 is forced out of the seafloor 50 by pumping water through the suction pump interface 23 into the suction pile 20. In particular, the pressure inside the suction pile 20 is increased to a point where the pile 20 is driven out of the seafloor 50. Because the shear blade 15 is not retracted, the sheared portion 42 of the well head 40 is retained within the well head conductor receptacle 36 of the suction pile 20 and thereby removed from the seafloor 50 with the embedded shear 100.

While this disclosure has described certain embodiments of an embedded shear and generally associated methods, alterations, and permutations of these embodiments and methods will be apparent to those skilled in the art. Accordingly, the above description of example embodiments does not define or constrain this disclosure. Other changes, substitutions, and alterations are also possible without departing from the spirit and scope of this disclosure and the following claims. 

1. An embedded shear comprising: a pile; and a shear cutter integrated into the pile.
 2. The embedded shear of claim 1 wherein: the pile is a suction pile.
 3. The embedded shear of claim 2 wherein: the pile further comprises a pump interface.
 4. The embedded shear of claim 1 wherein: the shear cutter is hydraulically activated.
 5. The embedded shear of claim 4 wherein: the shear cutter further comprises hydraulic cylinders driven by external hydraulic power.
 6. The embedded shear of claim 5 wherein: the external hydraulic power is supplied by one of a hydraulic umbilical, an accumulator bottle or a remotely operated vehicle hot stab.
 7. The embedded shear of claim 1 wherein: the pile further comprises a well head conductor receptacle adapted to receive a subsea well head.
 8. The embedded shear of claim 7 wherein: the shear cutter further comprises a shear blade that extends across the well head conductor receptacle when activated.
 9. The embedded shear of claim 1 wherein: the shear cutter is mounted within the pile near a lower end thereof.
 10. A method for removing a subsea well head comprising: providing a pile with a shear cutter integrated therein; lowering the pile over the well head; pumping water out of the pile to drive the pile into the seafloor to a desired cutting depth; activating the shear cutter to cut off a portion of the well head; and pumping water into the pile to drive the pile out of the seafloor.
 11. The method of claim 10 wherein: activating the shear cutter comprises providing hydraulic power to hydraulic cylinders to drive a shear blade.
 12. The method of claim 10 further comprising: receiving the well head within a well head conductor receptacle of the pile while lowering the pile over the well head.
 13. The method of claim 12 wherein: activating the shear cutter comprises driving a shear blade across the well head conductor receptacle to cut off the portion of the well head.
 14. The method of claim 13 further comprising: retaining the cut off portion of the well head within the well head conductor receptacle.
 15. The method of claim 14 further comprising: raising the pile away from the seafloor while retaining the cut off portion of the well head therein.
 16. A method for removing a subsea well head comprising: providing a pile with a shear cutter mounted internally near a lower end thereof; lowering the pile over the well head; embedding the pile into the seafloor to a desired cutting depth without excavating a glory hole; activating the shear cutter to cut off a portion of the well head; and removing the pile from the seafloor.
 17. The method of claim 16 further comprising: raising the pile away from the seafloor while retaining the cut off portion of the well head therein.
 18. The method of claim 16 wherein: embedding the pile into the seafloor comprises pumping water out of the pile; and removing the pile from the seafloor comprises pumping water into the pile.
 19. The method of claim 16 further comprising: receiving the well head within a well head conductor receptacle of the pile while lowering the pile over the well head.
 20. The method of claim 19 wherein: activating the shear cutter comprises driving a shear blade across the well head conductor receptacle to cut off the portion of the well head. 